1. Field of the Invention
This invention relates to a chain of fuse-links each of which composes a fuse assembly used for large electric current and to a forming method of the same.
2. Description of the Prior Art
A fuse assembly named a fusible link and used for large electric current has a structure shown in FIGS. 5 and 6.
In the Figures, designated 21 is a fuse-link that includes an arc-shaped fusing portion 22 provided with a couple of terminal portions 23, 23 at both ends thereof, the terminal portions 23, 23 being disposed to constitute a pair of wing-shaped members. Further, on the top of the fusing portion 22 a low-melting alloy piece 25 is fixed by a pair of crimping members 24, 24.
The fuse-link 21 with a spacer 26 is received in a housing 27 made of a synthetic resin and covered by a covering plate 28 to compose a fuse assembly 29 used for large electric current.
In FIGS. 7 to 9, there is shown a conventional forming method of the fuse-link 21. First, as shown in FIG. 7, in an initial process of a first production line, a plate material made of an electrically conductive metal such as copper and beryllium-copper alloy is punched to obtain a primary formed product P1. The primary formed product P1 has a narrow-strip-shaped fusing portion 22 provided with a crimping member 24 at both sides thereof. Further, a couple of aligned terminal portions 23, 23 with a hole 23a are respectively positioned at each end of the fusing portion 22 by way of a retaining plate 30. Each terminal portion 23 is connected to a carrier strap 32 (continuous band plate) by a connection piece 31 so that the products P1 are continuously connected. In the next step, at the middle portion of the fusing portion 22 there is mounted a low-melting alloy piece 25 to be fixed by bending the crimping members 24, 24 so as to obtain a secondary formed product P2.
Then, a large number of the secondary formed products P2 continuously connected by the carrier strap 32 disposed at both sides thereof are wound in a reel 33 to be stored as shown in FIG. 8.
Next, before assembling the fuse assembly 29 for large electric current, a second production line, as shown in FIGS. 9A and 9B, cuts the connection piece 31 to separate the fuse-links from the carrier strap 32. Then, both the retaining plates 30, 30 are bent into arc shape so that the low-melting alloy piece 25 is positioned in the top position to obtain a finished product of a fuse-link 21.
The prior art for forming fuse-links 21, as shown in FIGS. 7 to 9, has the two separate production process lines to protect the fusing portions 22, which brings a high production cost and has a disadvantage that it needs two steps for quality control and also for inventory control.